What the Science Says About the Safety and Side Effects of Probiotics
Whether probiotics are likely to be safe for you depends on your health.
- In people who are generally healthy, probiotics have a good safety record. Side effects, if any, usually consist only of mild digestive symptoms such as gas.
- On the other hand, there have been reports linking probiotics to severe side effects, including dangerous infections, in people with serious underlying medical problems.
- People most at risk include the critically ill, those who have had surgery, very sick infants, and people with weakened immune systems.
Even for healthy people, there are uncertainties about the safety of probiotics. Most of our knowledge about safety comes from studies of Lactobacillus and Bifidobacterium. Less is known about other probiotics. Also, information on the long-term safety of probiotics is limited, and safety may differ from one type of probiotic to another.
For example, even though a National Center for Complementary and Integrative Health-funded study showed that a particular kind of Lactobacillus appears to be safe in healthy adults age 65 and older, this does not mean that all probiotics containing Lactobacillus would be safe for people in this age group.
Are Probiotics Good for Your Health?
Probiotics are gaining in popularity, and chances are you've heard about them as "good bacteria" or seen them advertised in your supermarket's yogurt aisle. But what are probiotics, and do they have any real health benefits?
Probiotics are live microorganisms—bacteria, for example—that are
either the same or similar to microorganisms found naturally in our bodies. Although
we tend to think of bacteria as harmful "germs," many bacteria actually
help the body function properly. Probiotics are available as dietary supplements and
in dairy foods, and our research tells us that probiotics/prebiotics are among the
top five natural products used by both adults and children. It is important to note
that the U.S. Food and Drug Administration has not approved any health claims for
probiotics; however, there is some evidence that probiotics may be helpful for
conditions such as diarrhea caused by antibiotics and infections, as well as
symptoms of irritable bowel syndrome.
— Josephine P. Briggs, MD
NIH Supports Research on Probiotic Products
The National Institutes of Health has established the Human Microbiome Project to study the many microorganisms and their genes (called the "microbiome") that share our body space. These microbes outnumber our own cells by 10 to 1 and one of the most important things they do for us is to help with digestion. Part of this project is an initiative to study probiotic products, including their health benefits, how they work, and their long-term effects. Several NIH agencies are involved in this effort. For example, the National Institute of Diabetes and Digestive and Kidney Diseases is encouraging new research projects to study probiotics and the development of diseases such as inflammatory bowel disease, obesity, and diabetes.